I love MSN and it's one of my favourite Instant Messaging tools for fun but... try to imagine this situation:
You're using an Instant Messaging (IM) tool for a communication between coworkers in different places around the world and you've an ADSL connection in your office. You start your IM program and you're ready to communicate with all your contacts. The communication works good for hours but at a certain moment your ADSL provider has a DNS problem. What happens now?
If your IM program is MSN (but this happens also for Yahoo Messenger or Skype for example) you're out... you cannot reach your contact until the network problem is solved.
If you're using GTalk, you're again in contact with your friends around the world and you don't see the network problem... GTalk is working!
Why this?
MSN uses a protocol that is a variant of the SIP protocol. The Session Initiation Protocol (SIP) uses DNS procedures to allow a client to resolve a SIP Uniform Resource Identifier (URI) into the IP address, port, and transport protocol of the next hop to contact. It also uses DNS to allow a server to send a response to a backup client if the primary client has failed.
GTalk instead uses XMPP. When it starts, it opens a socket and after the connection is established, the socket remains opened until you close the program. GTalk does an XMPP authentication over a socket using a Google generated token and this ensures that you can work also without the DNS.
This is what occours on my system... I've a temporary DNS problem with my provider, MSN is down and GTalk is up and running (with a big smile)!! 